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→Muddy (J) Sandstone
===Muddy (J) Sandstone===
===Muddy (J) Sandstone===
The Muddy (J) Sandstone ranges in thickness from 40 to 150 ft across Wattenberg Field and consists of two members: an older Fort Collins Member and a younger Horsetooth Member<ref name=WeimSon1982 /><ref name=WeimSon1989 /><ref> MacKenzie, D. B., 1965, [https://archives.datapages.com/data/bulletns/1965-67/data/pg/0049/0002/0150/0186.htm Depositional environments of Muddy Sandstone, western Denver basin, Colorado]: AAPG Bulletin, v. 49, p. 186–206.</ref><ref> Weimer, R. J., S. A. Sonnenberg, G. B. C. Young, 1986, [https://archives.datapages.com/data/specpubs/resmi1/data/a066/a066/0001/0100/0143.htm Wattenberg Field, Denver Basin, Colorado], ‘’in’’ C. W. Spencer, and R. F. Mast, eds., Geology of tight gas reservoirs: [https://archives.datapages.com/data/alt-browse/aapg-special-volumes/sg24.htm AAPG Studies in Geology 24], p. 143–164.</ref> ([[:file:M125-WattenbergField-Figure7.jpg|Figures 7]], ([[:file:M125-WattenbergField-Figure10.jpg|10]], [[file:M125-WattenbergField-Figure11.jpg|11]], ([[:file:M125-WattenbergField-Figure12.jpg|12]]). The Fort Collins consists of very fine- to fine-grained sandstone containing marine trace fossils and is interpreted to be a delta front deposit. The Horsetooth consists of fine- to medium-grained, well-sorted, cross-stratified sandstone. This sandstone is interpreted to have been deposited as part of a valley-fill deposit of fresh to brackish water origin. The sandstones contain carbonized wood fragments and are intercalated with siltstone and mudstone. The valley-fill model is shown in [[:file:M125-WattenbergField-Figure13.jpg|Figure 13]]. The sequence stratigraphy of the Muddy (J) Sandstone reservoir in Wattenberg field was discussed in detail by Weimer and Sonnenberg<ref name=WeimSon1989 />. Regional distribution of the Muddy (J) and valley-fill systems have been published by Weimer and Sonnenberg<ref name=WeimSon1989 />, Dolson et al.<ref> Dolson, J. C., D. S. Muller, M. J. Evetts, and J. Stein, 1991, [https://archives.datapages.com/data/bulletns/1990-91/data/pg/0075/0003/0000/0409.htm Regional paleotopographic trends and production, Muddy Sandstone (Lower Cretaceous), Central and Northern Rocky Mountains]: AAPG Bulletin, v. 75, no. 3, p. 409–435.</ref>, and others.
The Muddy (J) Sandstone ranges in thickness from 40 to 150 ft across Wattenberg Field and consists of two members: an older Fort Collins Member and a younger Horsetooth Member<ref name=WeimSon1982 /><ref name=WeimSon1989 /><ref> MacKenzie, D. B., 1965, [https://archives.datapages.com/data/bulletns/1965-67/data/pg/0049/0002/0150/0186.htm Depositional environments of Muddy Sandstone, western Denver basin, Colorado]: AAPG Bulletin, v. 49, p. 186–206.</ref><ref> Weimer, R. J., S. A. Sonnenberg, G. B. C. Young, 1986, [https://archives.datapages.com/data/specpubs/resmi1/data/a066/a066/0001/0100/0143.htm Wattenberg Field, Denver Basin, Colorado], ‘’in’’ C. W. Spencer, and R. F. Mast, eds., Geology of tight gas reservoirs: [https://archives.datapages.com/data/alt-browse/aapg-special-volumes/sg24.htm AAPG Studies in Geology 24], p. 143–164.</ref> ([[:file:M125-WattenbergField-Figure7.jpg|Figures 7]], [[:file:M125-WattenbergField-Figure10.jpg|10]], [[:file:M125-WattenbergField-Figure11.jpg|11]], ([[:file:M125-WattenbergField-Figure12.jpg|12]]). The Fort Collins consists of very fine- to fine-grained sandstone containing marine trace fossils and is interpreted to be a delta front deposit. The Horsetooth consists of fine- to medium-grained, well-sorted, cross-stratified sandstone. This sandstone is interpreted to have been deposited as part of a valley-fill deposit of fresh to brackish water origin. The sandstones contain carbonized wood fragments and are intercalated with siltstone and mudstone. The valley-fill model is shown in [[:file:M125-WattenbergField-Figure13.jpg|Figure 13]]. The sequence stratigraphy of the Muddy (J) Sandstone reservoir in Wattenberg field was discussed in detail by Weimer and Sonnenberg<ref name=WeimSon1989 />. Regional distribution of the Muddy (J) and valley-fill systems have been published by Weimer and Sonnenberg<ref name=WeimSon1989 />, Dolson et al.<ref> Dolson, J. C., D. S. Muller, M. J. Evetts, and J. Stein, 1991, [https://archives.datapages.com/data/bulletns/1990-91/data/pg/0075/0003/0000/0409.htm Regional paleotopographic trends and production, Muddy Sandstone (Lower Cretaceous), Central and Northern Rocky Mountains]: AAPG Bulletin, v. 75, no. 3, p. 409–435.</ref>, and others.
[[file:M125-WattenbergField-Figure10.jpg|center|framed|300 px|{{Figure number|10}}Type log for Wattenberg Field. Curves shown are gamma ray, spontaneous potential, resistivity, and neutron/density. Black bar in depth track indicates cored interval. Fort Collins Member designated F.C.M., and Horsetooth Member designated H.M. Note perforated interval 8160–8173 ft and associated neutron-density crossover gas effect.]]
[[file:M125-WattenbergField-Figure10.jpg|center|framed|300 px|{{Figure number|10}}Type log for Wattenberg Field. Curves shown are gamma ray, spontaneous potential, resistivity, and neutron/density. Black bar in depth track indicates cored interval. Fort Collins Member designated F.C.M., and Horsetooth Member designated H.M. Note perforated interval 8160–8173 ft and associated neutron-density crossover gas effect.]]